﻿#region Copyright notice and license

// Copyright 2019 The gRPC Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#endregion

using System;
using System.Threading;
using System.Threading.Channels;
using System.Threading.Tasks;
using Grpc.Core;

namespace Tests.UnitTests.Helpers
{
    public class TestAsyncStreamReader<T> : IAsyncStreamReader<T> where T : class
    {
        private readonly Channel<T> _channel;
        private readonly ServerCallContext _serverCallContext;

        public T Current { get; private set; } = null!;

        public TestAsyncStreamReader(ServerCallContext serverCallContext)
        {
            _channel = Channel.CreateUnbounded<T>();
            _serverCallContext = serverCallContext;
        }

        public void AddMessage(T message)
        {
            if (!_channel.Writer.TryWrite(message))
            {
                throw new InvalidOperationException("Unable to write message.");
            }
        }

        public void Complete()
        {
            _channel.Writer.Complete();
        }

        public async Task<bool> MoveNext(CancellationToken cancellationToken)
        {
            _serverCallContext.CancellationToken.ThrowIfCancellationRequested();

            if (await _channel.Reader.WaitToReadAsync() &&
                _channel.Reader.TryRead(out var message))
            {
                Current = message;
                return true;
            }
            else
            {
                Current = null!;
                return false;
            }
        }
    }
}
